In recent years, developments have proceeded on a TFT which uses a transparent oxide semiconductor as an active layer.
US2006/108636 A1 discloses a technology on a TFT which uses an amorphous transparent oxide semiconductor film (IGZO film) including In, Ga, Zn and O as an active layer.
The above described thin film transistor has received attention, because the film is transparent and can be formed at a low temperature, and a transparent TFT can be formed on a substrate having flexibility such as a plastic.
US2007/052025 A1 discloses a technology of enhancing environment stableness by providing a protection film on a TFT which has an amorphous IGZO film as an active layer.